The proposed work will deal with low density lipoprotein (LDL) receptors on the isolated perfused artery. The question why tryspin resistant (internalized?) low density lipoprotein (LDL) is temperature dependent, while tryspin resistant LDL (receptor bound?) is independent of temperature will be studied. Apparently internalization is an energy dependent process, receptor binding is not. This finding will be tested by exposing perfused vessels to metabolic inhibitors. In addition, possible binding of LDL in the arterial wall to collagen, elastin or glycosaminglycans will be investigated. The effect of 7-ketocholesterol (7-KC) on these parameters ("binding"? "internalization"?) will be studied. Using red cell ghosts and phospholipid vesicles as models, studies will be directed to characterize the effects of 7-KC on phospholipid bilayers and to extend these observations to the interaction between LDL containing phospholipid vesicles and red blood cell membrane.